MECOA's Model Engine Forum & Swap Shop

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What is the normal end gap for the ring at top of stroke for the KB 40 sportster. Just wondering how worn out mine is. Mine measures 12 thousands. I don't have a ridge at the top of the cyl so assuming the cyl is still in good condition.

K&B never made a Sporster 40. The Sportsters were 20, 28, 45, and 65's. None of them had a ring. They were AAC's in the sense that the cylinder was aluminum as was the piston and the piston was chrome plated.

Chuck may have that later version of the classic 4011 that was aimed more for sport fliers than the early CL Rat /RC Pylon howler versions. The one with bolt-on front and back ends, came in shaft rotary and rear disc rotary versions... and of course, you could switch exhaust stack left or right on those (preferably before running them in.) Those had Dykes rings.

I don't know the nominal gap spec, but if it is a 4011-based engine MECOA/K&B should still have replacement rings.

I have a box full of broken K&B 4011 engines. Probably enough parts to make one good engine. Most hit the pavement. Bent rods, broken crankcases etc. I've had them for years. Just couldn't bring myself to throw them away. There are good piston/cylinders and rings in the pile. Maybe someone can use them. let me know.